Which Countries do Not Use the Metric System?

Only three countries in the world have not officially adopted the metric system: Liberia, Myanmar and the United States. Though each country uses some metric measurements — for instance, in the U.S., many science-related measurements and medicine dosages are in metric units — each also uses a mixture of customary units.

More facts about metrification:

Before the 1960s, there was no actual standard metric system, rather, there were several variations. The modern standard metric system, denoted in SI units, came into being in 1960 and was adopted by most countries in the 1960s and 1970s.

The first metric system was actually designed on the orders of Louis XVI of France. Thomas Jefferson was a fan of the system and tried to get it adopted in the U.S., but the U.S. Congress declined it.

Even countries that are officially metric often have one or two surviving other measurements. For instance, in Brazil, Argentina and Australia, tire pressure is still measured in PSI — pounds of force per square inch — and property in Japan is often sold by the tsubo, a unit of measurement roughly equivalent to two tatami mats.